1. Field of the Invention
The invention relates to the field of personal safety and personnel location, particularly to a personal safety radio device which is carried by the person to be protected on a mounting device and includes a transmitter powered by a current source specific to the device and an antenna arrangement.
2. Prior Art
Radio apparatus for personal safety or work safety can be divided into two categories in accordance with their function. In one category, a self-excited transmitter, which as a rule is permanently active and which is carried by the person to be protected either in a shoe, a belt or when used underground in the cap lamp, serves to mark the person (German patent No. 2026167). The permanently active transmitter continuously emits a high frequency signal which actuates a signal receiver and the switching device connected thereto when it is received by a receiving antenna which as a rule is stationarily disposed in the danger or monitoring region. By reason of the constant energy consumption the operational life is limited even with modern, high-power batteries. The current source and its energy consumption constitute a considerable operational risk when continuously operated for long periods of time, particularly with devices for personal safety and for the location of people who are buried alive or trapped in underground operations, building works or in areas endangered by avalanches.
The second category relates to so-called passive danger signal transmitters without their own energy source. The danger signal transmitter includes a transceiver which is excited in a predetermined transmission range of a transmitter by a certain transmission frequency and emits a response signal on a different frequency. A danger signal receiver generates alarm or cut-off signals from the response frequency. The advantage of these devices resides in the independence of the transceiver of an energy supply. The substantial disadvantage of purely passive transceivers is known to lie in the fact that their transmission range is too small. Due to this disadvantage the use of purely passive transceivers for marking people who have been buried alive, particularly in underground operations, is too risky.